1. Field of the Invention
The present invention relates generally to exercising devices and more specifically to a plyometric exercising device which enables the development of the user's explosive reactive power.
2. Prior Art
Plyometrics is the systematic training of explosive reactive power. This type of power is that utilized when jumping downward from an elevated position, landing and then springing upward. Upon landing, leg muscles will load or stretch, also referred to as eccentric muscular contraction. When springing upward after landing, the leg muscles "explode" or shorten, also referred to as concentric muscular contraction. It is "explosive" power that the present invention develops in a user by, in effect, causing the same muscular contractions that would occur if the user were to jump from an elevated position under more controlled and adjustable conditions. Nothing in the prior art teaches a device which even approaches the same purpose as the present invention.
Explosive reactive power is especially crucial to athletes involved in sports such as football, running and jumping. Football linesmen and sprinters, for example, must be able to "explode" off the line and starting block, respectively. A weak start can ruin an entire race for a runner. There has never been an exercising device that specifically addressed this need to develop explosive reactive power--until that of the present invention.
Numerous exercising devices have appeared on the market in response to the fitness craze which has swept the United States and has now reached many other parts of the world. Such devices range from simple hand weights held while jogging to weight bars upon which weights of varying heaviness can be added or subtracted, to elaborate weightlifting systems which fill entire rooms with apparatus. While some prior art exercising devices gradually increase the weight against which the user must exert similarly increasing muscular force, none provide the sudden force of the present invention, which force develops explosive reactive power.
Several pneumatic and hydraulic exercising devices can be found among the prior art. As an example, Keiser, U.S. Pat. No. 4,257,593, discloses a pneumatic exercising device employing a source of compressed gas which is controllable and is used for variable resistance. Devices such as those taught in the Keiser patent merely perform the same basic function as traditional weight devices: they exert passive resistive force which must be overcome by the user's muscular force. By increasing the magnitude of the resistive force applied by any of the prior art devices, either by increasing the hydraulic or pneumatic pressure or by simply adding more weights onto a weight type device, a user can develop greater muscular force. None of these devices in any way employ active resistive force to develop explosive reactive power.
The present invention fulfills the need for an exercising device which uses active resistive force to develop explosive reactive power, such feature being totally absent from all prior art devices. The present invention plyometric exercising device generates a sudden downward force upon a weightlifting bar as the user moves it downward across a switch. This force is generated when the switch activates a source of compressed gas, which is adjustable according to the pressure desired by the user. The gas then fills cylinders whose pistons are attached to the weightlifting bar and causes a downward pull on the bar.